Mitsubishi Galant (2004+). Manual — part 1550
SRS AIR BAG DIAGNOSIS
TSB Revision
SUPPLEMENTAL RESTRAINT SYSTEM (SRS)
52B-93
CAUTION
If DTC B1411 <1st squib> or B1491 <2nd squib>
is set in the SRS-ECU, always diagnose the CAN
main bus line.
.
CIRCUIT OPERATION
• The SRS-ECU judges how severe a collision is
by detecting signals from the front impact sensors
and the front air bag analog G-sensor. If the
impact is over a predetermined level, the
SRS-ECU sends an ignition signal. At this time, if
the front air bag safing G-sensor is on, the SRS
air bag will inflate.
• The ignition signal is input to the air bag module
via the clock spring to inflate the air bag.
.
DTC SET CONDITIONS
This DTC is set if there is abnormal resistance
between the input terminals of the passenger’s air
bag module (squib). However, if no DTC reset, the
SRS warning light will be switched off (DTC will be
retained).
.
TROUBLESHOOTING HINTS
• Open circuit in the passenger's air bag module
(squib) circuit
• Improper connector contact
• Malfunction of the SRS-ECU
.
DIAGNOSIS
Required Special Tools:
• MB991958: Scan Tool (MUT-III Sub Assembly)
• MB991824: Vehicle Communication Interface (V.C.I.)
• MB991827: MUT-III USB Cable
• MB991910: MUT-III Main Harness A (Vehicles with CAN
Communication System)
• MB991865: Dummy resister
• MB991866: Resister harness
AC305362
CONNECTOR: C-121
C-121 (Y)
AD
SRS-ECU
SRS AIR BAG DIAGNOSIS
TSB Revision
SUPPLEMENTAL RESTRAINT SYSTEM (SRS)
52B-94
STEP 1. Using scan tool MB991958, diagnose the CAN bus
line.
CAUTION
To prevent damage to scan tool MB991958, always turn the
ignition switch to the "LOCK" (OFF) position before con-
necting or disconnecting scan tool MB991958.
(1) Connect scan tool MB991958. Refer to "How to connect the
scan tool
."
(2) Turn the ignition switch to the "ON" position.
(3) Diagnose the CAN bus line.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the CAN bus line found to be normal?
YES : Go to Step 2.
NO : Repair the CAN bus line (Refer to GROUP 54C,
STEP 2. Recheck for diagnostic trouble code.
Check again if the DTC is set.
(1) Erase the DTC.
(2) Turn the ignition switch to the "ON" position.
(3) Check if the DTC is set.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the DTC set?
YES : Go to Step 3.
NO : There is an intermittent malfunction such as poor
engaged connector(s) or open circuit (Refer to
GROUP 00, How to Cope with Intermittent
Malfunction
AC305412
AB
MB991910
DATA LINK
CONNECTOR
MB991824
MB991827
AC305412
AB
MB991910
DATA LINK
CONNECTOR
MB991824
MB991827
SRS AIR BAG DIAGNOSIS
TSB Revision
SUPPLEMENTAL RESTRAINT SYSTEM (SRS)
52B-95
STEP 3. Check the passenger's air bag module. (Using
scan tool MB991958, read the diagnostic trouble code.)
(1) Disconnect the negative battery terminal.
(2) Disconnect the passenger’s air bag module connector
C-110.
(3) Slide the outer housing of the clock spring side of
passenger’s air bag module connector C-110 in the arrow
direction shown, and disconnect the connector.
(4) Connect special tool MB991865 to special tool MB991866.
CAUTION
Do not insert a test probe into the terminal from its front
side directly, as the connector contact pressure may be
weakened.
(5) Insert special tool MB991866 into the harness side
connector C-110 (terminal No.1 and 2 <1st squib> or
terminal No.3 and 4 <2nd squib>) by backprobing.
(6) Connect the negative battery terminal.
(7) Erase the diagnostic trouble code memory, and check the
diagnostic trouble code.
Q: Is DTC B1411 <1st squib> or B1491 <2nd squib> set?
YES : Go to Step 4.
NO : Replace the passenger's air bag module. (Refer to
AC307137AC
C-110 (Y)
FRONT DECK
CROSSMEMBER
CONNECTOR: C-110
HARNESS SIDE
CONNECTOR
(REAR VIEW)
AC306561AD
OUTER HOUSING OF THE PASSENGER'S
AIR BAG MODULE CONNECTOR C-110
AC306760AB
MB991865 (DUMMY
RESISTOR: 3
Ω)
MB991866
(RESISTOR HARNESS)
C-110 HARNESS
CONNECTOR
C-110
PASSENGER'S
AIR BAG MODULE
CONNECTOR
SRS AIR BAG DIAGNOSIS
TSB Revision
SUPPLEMENTAL RESTRAINT SYSTEM (SRS)
52B-96
STEP 4. Check the harness for open circuit between
SRS-ECU connector C-121 (terminal No.27 and 28 <1st
squib> or terminal No.30 and 31 <2nd squib>) and the
passenger's air bag module connector C-110 (terminal
No.1 and 2 <1st squib> or terminal No.4 and 3 <2nd
squib>).
(1) Unclip passenger’s air bag module connector C-110.
(2) Disconnect SRS-ECU connector C-121 and passenger's air
bag module connector C-110.
CAUTION
Do not insert a test probe into the terminal from its front
side directly as the connector contact pressure may be
weakened.
(3) Check for continuity between the following terminals. It
should be less than 2 ohms.
<1st squib>
• SRS-ECU connector C-121 (terminal No.27) and the
passenger’s air bag module connector C-110 (terminal
No.1)
• SRS-ECU connector C-121 (terminal No.28) and the
passenger’s air bag module connector C-110 (terminal
No.2)
<2nd squib>
• SRS-ECU connector C-121 (terminal No.30) and the
passenger’s air bag module connector C-110 (terminal
No.3)
• SRS-ECU connector C-121 (terminal No.31) and the
passenger’s air bag module connector C-110 (terminal
No.4)
Q: Does continuity exist?
YES : Erase the diagnostic trouble code memory, and check
the diagnostic trouble code. If DTC B1411 <1st squib>
or B1491 <2nd squib> set, replace the SRS-ECU.
(Refer to
AC307137AC
C-110 (Y)
FRONT DECK
CROSSMEMBER
CONNECTOR: C-110
HARNESS SIDE
CONNECTOR
(REAR VIEW)
AC305362
CONNECTOR: C-121
C-121 (Y)
AH
SRS-ECU
C-121
HARNESS SIDE
CONNECTOR
(REAR VIEW)
42
31
38
27
21
41
28
39
22
30
25
47
36
33
44
34
45
37
48
26
29
23
40
32
43
35
46
24
B
A
AC308151
42
31
38
27
21
41
28
39
22
30
25
47
36
33
44
34
45
37
48
26
29
23
40
32
43
35
46
24
B
A
C-121
HARNESS SIDE
CONNECTOR
(REAR VIEW)
C-110
HARNESS SIDE
CONNECTOR
(REAR VIEW)
AB
<1ST SQUIB>
AC308152
42
31
38
27
21
41
28
39
22
30
25
47
36
33
44
34
45
37
48
26
29
23
40
32
43
35
46
24
B
A
C-121
HARNESS SIDE
CONNECTOR
(REAR VIEW)
C-110
HARNESS SIDE
CONNECTOR
(REAR VIEW)
AB
<2ND SQUIB>
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